1. Field of the Invention
This disclosure relates to a semiconductor module.
2. Description of the Prior Art
A system is configured in various electronic instruments by combining semiconductor modules having a plurality of semiconductor packages (or semiconductor chips) mounted on a printed circuit board.
As shown in FIG. 1, a conventional semiconductor module 10 has a plurality of semiconductor packages 30 mounted on at least one surface of a printed circuit board 20 with a flat shape. The semiconductor packages 30 are electrically connected by a wiring pattern on the printed circuit board 20. Contact terminals 24 are disposed along a long side of the printed circuit board 20 and are connected to a socket in an electronic instrument (not shown), thereby connecting the electronic instrument and the semiconductor packages. The socket is fabricated to have a length corresponding to the length of a long side of the printed circuit board 20 so that the printed circuit board 20 is inserted into and electrically connected to the socket.
Because the semiconductor packages 30 are two-dimensionally mounted, e.g., in co-planar relation, on the flat printed circuit board 20, the area of the printed circuit board 20 is increased in proportion to the number of mounted semiconductor packages 30. Accordingly, miniaturization is made difficult in the case of the semiconductor module 10 using the flat, e.g., planar, printed circuit board 20.
The length of the socket in an electronic instrument should also be increased when the length of the printed circuit board 20 is increased. Therefore, this acts as a limiting factor in the design of a motherboard in the electronic instrument and causes difficulties in the arrangement and wiring of other electronic parts.
As disclosed in U.S. Pat. No. 6,707,160, a three-dimensional semiconductor module utilizing a hollow cylindrical substrate carries wiring patterns. In addition, a central reinforcing body lies within the cylindrical substrate, but is composed of non-conductive insulating material and carries no signals. The three-dimensional semiconductor module has a structure in which at least one semiconductor chip is bent on the circumferential surface of the cylindrical substrate and connected thereto by bumps. For this, a surface of the semiconductor chip corresponding to the circumferential surface of the cylindrical substrate and carrying the bumps is bent in a concave shape.
Accordingly, the above three-dimensional semiconductor module has an advantage that the mounting area of the semiconductor module may be reduced. However, electrical characteristics may deteriorate because a stable grounding path is not easily secured. Thus, while in the above three-dimensional semiconductor module semiconductor chips mount around the cylindrical substrate in a relatively high mounting density, a stable grounding path and grounding area is not readily secured. More particularly, the grounding path is formed only through circuit wirings placed on the cylindrical substrate.
Furthermore, the manufacturing process of the three-dimensional semiconductor module is more complex than that of a conventional semiconductor module. To fabricate. the cylindrical substrate, a plate-shaped board is fabricated and subsequently bent in a cylindrical form, or the bent board is attached to the cylindrical reinforcing body. The plate-shaped semiconductor chip is fabricated and subsequently bent in shape corresponding to the curvature of the cylindrical substrate. The semiconductor chip may be broken in the case that stress is excessively concentrated in the central part of the semiconductor chip during the fabrication process, e.g., when bending semiconductor chip.
Also, the bent semiconductor chip shows a tendency to return to its original flat plate-shaped form. The shape-restoration energy increases especially near the edges of the semiconductor chip, and thereby deteriorates the ability of the bumps to couple to the cylindrical substrate.
As noted, when the semiconductor chip is bent the surface thereof formed with bumps is bent in a concave shape. As a result, the pitch of the bump patterns in the bent-shape form of the semiconductor chip is smaller than those in the plate-shaped form of semiconductor chip. Accordingly, electrical short circuits may occur between the bumps of the bent-shaped form of the semiconductor chips during the mounting of the bent-form semiconductor chips upon the cylindrical substrate.
Problems caused by heat generation may also occur. Because a plurality of the bent semiconductor chips are mounted around the cylindrical substrate, having insulating properties. The mounting density and corresponding heat concentration is high while the capability of heat dissipation decreases. As a result, the performance of the three-dimensional semiconductor module may be reduced, e.g., due to the reinforcing body having insulating properties.